我在 AWS 上的 DC/OS (Mesos) 集群上安装了 Kafka。启用三个代理并创建一个名为“topic1”的主题。
dcos kafka topic create topic1 --partitions 3 --replication 3
然后我编写了一个 Producer 类来发送消息,并编写了一个 Consumer 类来接收消息。
public class Producer {
public static void sendMessage(String msg) throws InterruptedException, ExecutionException {
Map<String, Object> producerConfig = new HashMap<>();
System.out.println("setting Producerconfig.");
producerConfig.put("bootstrap.servers",
"172.16.20.207:9946,172.16.20.234:9125,172.16.20.36:9636");
ByteArraySerializer serializer = new ByteArraySerializer();
System.out.println("Creating KafkaProcuder");
KafkaProducer<byte[], byte[]> kafkaProducer = new KafkaProducer<>(producerConfig, serializer, serializer);
for (int i = 0; i < 100; i++) {
String msgstr = msg + i;
byte[] message = msgstr.getBytes();
ProducerRecord<byte[], byte[]> record = new ProducerRecord<>("topic1", message);
System.out.println("Sent:" + msgstr);
kafkaProducer.send(record);
}
kafkaProducer.close();
}
public static void main(String[] args) throws InterruptedException, ExecutionException {
sendMessage("Kafka test message 2/27 3:32");
}
}
public class Consumer {
public static String getMessage() {
Map<String, Object> consumerConfig = new HashMap<>();
consumerConfig.put("bootstrap.servers",
"172.16.20.207:9946,172.16.20.234:9125,172.16.20.36:9636");
consumerConfig.put("group.id", "dj-group");
consumerConfig.put("enable.auto.commit", "true");
consumerConfig.put("auto.offset.reset", "earliest");
ByteArrayDeserializer deserializer = new ByteArrayDeserializer();
KafkaConsumer<byte[], byte[]> kafkaConsumer = new KafkaConsumer<>(consumerConfig, deserializer, deserializer);
kafkaConsumer.subscribe(Arrays.asList("topic1"));
while (true) {
ConsumerRecords<byte[], byte[]> records = kafkaConsumer.poll(100);
System.out.println(records.count() + " of records received.");
for (ConsumerRecord<byte[], byte[]> record : records) {
System.out.println(Arrays.toString(record.value()));
}
}
}
public static void main(String[] args) {
getMessage();
}
}
首先我跑了Producer
在集群上将消息发送到topic1
。然而当我跑的时候Consumer
,它无法接收任何东西,只是挂起。
Producer
正在工作,因为我能够通过运行 Kafka 安装附带的 shell 脚本来获取所有消息
./bin/kafka-console-consumer.sh --zookeeper master.mesos:2181/dcos-service-kafka --topic topic1 --from-beginning
但为什么我不能接收Consumer
? This post https://github.com/SOHU-Co/kafka-node/issues/11建议具有旧偏移量的 group.id 可能是一个可能的原因。我只在消费者中而不是生产者中创建 group.id 。如何配置该组的偏移量?